Telephone-exchange system



'0. MQTAGGART.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 0m. 2s, 19l8.

1,355,926. I Pafented Oct. 19,1920.

W -mm I //4 van/on- Dawsan/V. 727774 A/ry.

UNITED STATES PATENT OFFICIE.

DAWSON TAGGAET, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION 01" NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Oct. 19, 1920.

Application filed October 23, 1918. Serial No; 259,367.

a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to those in which trunk circuits are employed in completing connections between telephone lines terminating at telephone switchboards or ofiices. I

In such systems it is desirable to provide signaling means whereby the operators handling the connections are definitely advised as to the status of the called telephone station. Especially in systems employing operator controlled means for signaling the desired station it is very desirable that the completing or trunk operator should receive an accurate indication that such station has answered.

It is the object of the present invention to provide an improved signaling system of this character which is simple and inexpensive and which provides a signaling means which, although unaffected by the,

changes in the electrical characteristics of the trunk circuit and the connected line circuit, incident to the establishment of the telephonic connection, will furnish an accurate signal upon the response of the called station.

To attain this object in accordance with the feature of the invention, the locking of the usual ringing signal control relay of a trunk circuit for indicating the response of the called station is controlled by means, associated with the signaling device, for preventing a premature indication being given, due to incidental momentary operations of the controlling supervisory relay prior to the answer of the called station.

The nature of this invention will fully appear from the following specification and the annexed drawing in which the figure shows diagrammatically a trunk circuit embodying the invention, together with suflicient portions of line and link circuits for cooperation therewith, to properly illustratc the operation of such. a system.

In the accompanying drawing, a trunk circuit B interconnects the switchboards or ofiices X and Y, terminating at office Y in i a plug 1 and at oflice X in a jack 2. An ordinary line circuit equipped with the usual line relay 3, cut-off relay 20 and line signal 4:, and terminating in a jack 5, connects an ordinary subscribers station C with oilice Y. A connecting or link circuit A, of any usual type, is provided at oflice X and terminates in plug 6 for connection with the jack 2 of the trunk circuit B. All portions of the link circuit A, not essential to the proper understanding of the invention,

have been omitted. The trunk circuit B is equipped with a ringing key 7, a supervisory relay 8, a trunk relay 9 and a signal control relay 10, which relays cooperate to control a ringing and guard signaling lamp 11 and a disconnect signaling lamp 19. As-

sociated with the signaling lamp 11, and

connected in parallel therewith, is a slow release relay 12 controlling the locking circult of the signal control relay 10.

It is thought that the invention may be, more fully comprehended from the following description of the operation of the system shown. 9

Assuming that the operator at switchboard X desires to call station C on the line circuit terminating in ack 5, at the switchboard Y, the operator at switchboard Y is notified in some suitable manner over a call circuit or otherwise and assigns the trunk circuit B. The operator at switchboard X thereupon inserts plug 6 of the link circuit A into the ack 2 of the; trunk circuit B.

The lamp 13 is lighted over a circuit ex-.

tending from battery through the lamp 13, the resistance 14 and the sleeve contacts of plug 6 and jack 2, to ground. Relay 9 is also operated over a circuit extending from battery through the winding of, relay 15, the ring contacts of plug 6 and jack 2, the windings of relay 9 in series, the tip contacts of jack2 and plug 6, to ground. However, due to the high resistance of the windings of relay 9 in series the supervisory relay 15 of the link circuit A is not operated at this time. The operation of relay 9 causes the lightingof lamp 11 over a circuit extending from battery through the lamp 11, the normal contact of relay 10 and the alternate contact of relay 9, to ground. Relay 12 is also operated over a circuit extending from battery through the winding of relay 12, the normal contactof relay 10 and the alterand 16, over a circuit extending from battery through the winding: of relay 16, the sleeve contacts of plug 1 and jack 5 and the winding of relay 20, to ground. The operation of relay 2O thereupon removes the line relay 3 and its associated line signal 4: fro1 n their normal association with the line circuit leading to station C. The relay 16, 1n closing its upper contact, establishes the continuity of the tip conductor of the trunk circuit. i

The operator at switchboard Y actuates the ringing key 7 which, in the usual manner, impresses signaling current upon the conductors of the line circuit associated with the station C to cause the operation of the usual signaling device at the called station. The ringing key 7, being released, after the signal at the called station has been operated, the trunk circult apparatus is 111 condition to respond to the answer of the called station. Upon the response of such station the supervisory relay 8 is operated over a circuit extending from battery through the winding ofrelay 8, the lower normal contact of ringing key 7, the ring contacts or plug 1 and jack 5, through the apparatus at the called station, the tip contacts oi:

, jack 5 and plug 1 and the upper alternate operates due to the current flowing through switchboard X may now converse with the 'its left-hand winding and in opening its normal contact opens the circuits of lamp 11 and of relay 12. However, the locking circuit of relay 10 is not completed until slow release relay 12 has fully released. Upon the complete release of relay 12, the relay lOis looked over a circuit extending from battery through the lower contact of relay 16, the right-hand winding of relay 10, the normal contact of relay 12, the alternate contact of relay 10 and the alternate contact of relay 9, to ground. The operator at station C through the operation of the usual listening key 17. Upon the completion of ;the conversation between the calling subscriber and the subscriber at station C the operator at switchboard X removes the plug 6 from the jack 2, thereby restoring the apparatus associated withthe link circuit A to its normal condition and releasing relay 9 to cause the lighting or the disconnect lamp 19 over a circuit established from battery through the lower contact of relay 16,

lay 9, to ground. Upon observing the lighted condition of lamp 19, the operator at the switchboard Y removes the plug 1 from the jack 5, thereby restoring all of the the lamp 119 and the normal contact of re 7 trunk circuit apparatus to normal condition. 7

While the called station is being signaled, the condenser 18 thereat becomes charged and, upon the release of the "ringing key 7 a discharge may take place through the winding oi supervisory relay 8, causing the momentary operation of such relay. Al-

though a corresponding momentary operat1 on of relay 10 is produced thereby, the ringing signal lamp 11 is not completely extinguished, due to thefact that the slow release relay 12 controls the: locking circuit of relay 10 in such a way that relay 10 is not locked in its operated position until relay 12 has fully released. Thus no false signal is produced by the dischargeof the capacitance of the linev circuit upon the release of the ringing key '7 prior to the answer of the called station.

What is claimed is: r r

1. In a telephone exchange system, a line clrcuit, a station thereon, a trunk circuit for connection therewith, a signal-control relay, a supervisory relay operating upon the an: swer of the station in response to a call originated by the trunk circuit to operate the s gnal control relay,.means for locking the signal control relay upon the operation thereof a signaling device operable uponthe locking of the signal control relay, and 7 means associated therewith to prevent the locking of the signal control relay upon the momentary operation thereof.

2. In a telephone exchange system, a line circuit, a station thereon, a trunk circuitfor connection therewith, a signal control relay, 7

a signaling device controlled thereby, a supervisory relay'operating upon the answer of the station in response to a call when the trunk circuit isjconnected with the line circuit, said supervisory relay operating the 7 signal control relay to cause a signal to be given by the signaling device, means for locking the signal control relay upon the op eration thereof, and means associated with the signaling device-for controlling the lock-' ing of thecontrol relay to prevent the signal being given by the signaling device upon an incidental operation of the supervisory relay. 7 V

3. In a telephoneexchange system, a line' circuit having capacitance, a station thereon, a trunk circuit for connection therewith, a-

signal control relay responsive either to the answer of the called station or to the discharge of the capacitance, a locking winding for the signal control relay, a signaling device adapted to produce a signal upon the energization of the locking winding, and a slow release relay for preventing the energization of the locking winding upon the discharge of the capacitance.

4. In a telephone exchange system, a line circuit, a station thereon, a trunk circuit for connection therewith, a signal control relay operating upon the response of the called station, a signaling device controlled there by, a slow release relay associated with the the signal control relay completed upon the release of the slow release relay to cause a signal to be given by the signaling device.

In witness whereof, I hereunto subscribe my name this 18th day of October, A. D., 1918.

DAWSON M. TAGGART.

signaling device, and a locking circuit for 

